I have an asphalt shingled roof with a serious problem. Due to a cathedral ceiling with exposed decking inside, part of the roof has insulation on top of the roof deck. As nearly as I can tell, during the last roof repair, part of the insulation was replaced with styrofoam. That’s right, white, beady styrofoam. The shingles were installed directly over the foam.

Well, over the years the foam has compressed (nails are sticking up above the shingles by 1" everywhere) and the roof is leaking everywhere. I was hoping to effect a temporary repair using asphalt roll roofing and cold lap cement. I want to cover the entire leaking area (about 60 sq. ft.) with the roll roofing, overlapping the good roof on either side and above by at least one foot, and sealing the new material to the old roofing around the edges of the patch with the lap cement. I would also seal each strip of new roofing to the layer below with the lap cement.

Does this idea have a chance of working? I’m looking for a few months, while I research how this roof should be re-insulated, repaired, and then reroofed.

There are a couple of ways you could insulate your roof, and still use shingles when you are ready to replace it. First, you could use wood sleepers installed to line up over the rafters of your cathedral ceiling, insulate between the sleepers with 1 1/2 inch thick polyisocyanurate insulation, and then install plywood decking overtop the sleepers and insulation, fastened to the sleepers. This would give you a substrate to nail to that won’t penetrate the ceiling below. The other option is to use a composite nailboard that consists of insulation and OSB, and adhere it to the roof deck with a product such as Insta-Stik.

I can probably come up with a couple other options, but for now those are my best recommendations. BTW, where is your house located?

If you do your repair right, based on the information you provided, it has a chance of working. Of course, you need to do something with the nails that are sticking up.

It would help more if you could provide a photo, but if I understand what you are going to do it certainly can’t make matters worse.

One question I have is are you really talking about using 90# roll roofing, or are you going to use a granule-surfaced mod bit? Secondly, are you going to use plastic roof cement for the laps, or are you going to use a cold adhesive? And last, you do plan on adhering the membrane down over the shingles and not just at the laps, right? You mentioned it was a 60 sq ft area, but is it 1 x 06, 2 x 30, 3 x 20???

The shingles I am planning to cover are so wavy that I can’t see sealing the roofing to them. I want to overlap the new roofing over the flat shingles on either side and above the bad area by about 1 foot and sealing the new roofing to the old there. And of course sealing each new layer to the course below. And I will pull any of the nails that stick up.

The area is about 8’ x 8’, so I would wind up covering about 10’ x 10’ with the new material.

First, you could use wood sleepers installed to line up over the rafters of your cathedral ceiling, insulate between the sleepers with 1 1/2 inch thick polyisocyanurate insulation, and then install plywood decking overtop the sleepers and insulation, fastened to the sleepers.

Cerberus can he or she have the insulation sheated without sleepers and just
screw the plywood down with long fasteners into the rafters?? We do it like that all the time .

Without knowing the particulars about the roof, I’d say that you could install insulation and plywood that is screwed down overtop the insulation. First of all, you would have to take great care that your screws were lining up with the rafters so they aren’t exposed on the underside of the cathedral ceiling. Naturally, you would want to use an insulation with a relatively high compressive strength like iso or even extrude polystyrene. Of course, in case of fire the polystyrene I believe turns into a poisonous gas when it burns, so I’d probably shy away from using it. Also, I’d recommend picture framing the roof with a wood nailer installed around the perimeter, so if you use 2x4’s the insulation should also be a nominal 1.5-inches thick.

With regard to screwing down the plywood, I’d recommend a coarse-threaded wood decking screw that can be countersunk into the plywood.